The present invention relates to an automatic conveyor apparatus for conveying semiconductor substrates and positioning the substrates correctly in a predetermined position. More particularly, the present invention relates to a pre-alignment apparatus for use in a conveyor system for conveying a substrate having a pattern such as an integrated circuit formed thereon to a pattern examination station in which the substrate is to be placed in a predetermined position relative to an optical apparatus by which the pattern is examined.
At the last step of the known manufacturing process of integrated circuits such as LSI or VLSI, the very fine pattern of the integrated circuit formed on a substrate such as a semiconductor wafer is examined by use of an optical apparatus such as a microscope. In order to increase the efficiency of pattern examination there has been used an automatic conveyor system which is able to correctly place the semiconductor substrate on the stage of an optical apparatus in a determined position and in a determined orientation. Such automatic conveyor system conventionally used for this purpose is generally provided with rotating rollers in contact with the outer circumference of the substrate and a photo-electric detector. At the prealignment step, the substrate is held by the rotating rollers and also rotated by the rollers in the circumferential direction. During the time the substrate is rotated, the photo-electric detector watches the peripheral shape of the substrate to set the position and orientation of the substrate as required.
In pre-alignment of the substrate by the known apparatus no problem occurs so long as all of the substrates to be examined have the same shape and the same size according to the same standard. However, if the substrates have different sizes and shapes according to different standards, then a precise adjustment of the position of the photo-electric detector is required. Otherwise, any pre-alignment with high accuracy is no longer possible. This adjustment of the position of the detector has to be made every time the size of the substrate to be conveyed is changed. Obviously, this is time consuming and reduces the efficiency of the examination work.